Multi-layered films are useful in forming hermetic seals, protecting packaged food products from loss of flavor, staleness, or spoilage due to light, oxygen and moisture. In addition, multi-layered films prevent undesirable leaching of the product to the outside of the film. For example, oily food products have the potential for some oil to leach out of the package.
Currently, extrusion houses purchase petroleum-based polymer films from commercial sources. These houses then nip laminate the polymer film to rigid petroleum based or polymeric sheets during production, forming barrier or non-barrier sheets, films or structures. Such petroleum-based films are unsuitable for thermal lamination systems currently in use when the extruded rigid stock is biopolymer based sheet, as the petroleum-based films do not adhere well to biopolymers and do separate from the biopolymers after a few weeks.
One approach to the problem has been to use adhesive bonding to join biopolymer material to traditional petrochemical packaging stock. Unfortunately, most rigid fabrication facilities lack the equipment for adhesive bonding. Adhesive bonding also adds steps to the fabrication process, increasing the complexity of and time for fabrication. Thus, adhesive bonding increases capital and production costs, and reduces run speeds.
For the foregoing reasons, it would be desirable to have a film for thermal adhesion to a rigid biopolymer structure that solves the above problems.